Royjak, could be strategy on the part of your opponents to break down the oil pattern on your line. Nothing wrong with that or if they see its working for you, they are trying it themselves. I have done this to opponents and have had opponents and teammates do it as well. If you are hitting a certain line and its working and they are struggling with their shot, who wouldnt try it? If it doesn't work for them, they are still trying to compete by taking your shot away or being patient hoping their shot will come in on that line. Sometimes bowlers have to be patient and let the shot come to them and for some it means the oil needs to be broken down more than for others. It is about the only way to play defense in bowling. Remember its a game and if its a tournament or a league it is a competition with the objective being to win and do your best so dont feel dissed. Actually consider it a compliment, you have figured out the shot and they are just trying to do what you are having success with and compete with you even if it means breaking down your shot.
HM
